The present invention relates to an ink jet printer for printing by jetting ink droplets, and more particularly relates to a maintenance station employed therewith to cap and apply suction to a nozzle of an ink jet head in order to achieve and maintain printing quality.
Non-impact recording methods recently have been employed because printing noise is reduced and such methods are suitable for color printing. Many new ink jet printers employ such methods and provide high speed recording and can be employed to be an ordinary paper. Drop-on-demand type ink jet printers widely are used as output equipment of personal computers because means for recovering waste ink are unnecessary and because such type printer can be miniaturized and of simple structure. This type of ink jet printer may be divided roughly into the heat machine transformation type and the electric machine transformation type.
The heat machine transformation type has an electric circuit mounted along the path of liquid passing to a nozzle. Ink is ejected by steam pressure on applying electric current and heat. This type of ink jet printer is suitable for miniaturization. However, scorching can occur over long periods of use. Therefore, special ink must be used to prevent such scorching.
The electric machine transformation type uses deformation occurring by applying an electric field to energy supply means in the form of a piezoelectric element. Use is not limited to a particular ink and this ink which is most suitable to obtain quality printing for a particular use can be employed. This type printer however requires a large space for the energy supply means and therefore is not suitable for miniaturization.
For resolving this problem, an ink jet for supplying energy to liquid by deformation of a side wall by utilizing electric deformation of a shear mode type is shown in Japanese Laid Open Patent Application 150355/1990. The most important feature is to give eject energy to liquid by deformation of a side wall which opens to a nozzle. Therefore, liquid paths may be arranged in a plane with an interval between nozzles.
In such ink jet printer, when an ink jet head is changed, when the printer is started after a long period of time, or when printing quality is reduced during printing, old ink is exhausted from the ink jet head by applying suction to a nozzle hole from a rubber cap pressed to a face of a plate of the nozzle. The circumference of the cap is pressed against the nozzle plate to seal the interior of the cap. At such time, an interior volume of the cap is reduced. Since air flows in the ink jet head from a nozzle hole, the cap interior is opened to the atmosphere in advance to eject a droplet. Next, the cap interior is shut off from the atmosphere for suctioning the ink jet head through the cap by a pump under airtight conditions. When the cap is detached from the nozzle plate, the cap interior is opened to the atmosphere to prevent a pressure drop therein. A pressure drop in the cap interior would cause poor election of an ink droplet because ink passing from the nozzle would adhere to the surface of the nozzle plate.
Therefore, such a maintenance station which is used for recovering ink quality includes a cap, an atmosphere opening valve, a pump, cams for driving such elements and a vacuum pipe. Such construction is complicated.
A maintenance station disclosed is Japanese Laid Open Patent Application 87267/1991 is shown in FIG. 56 and includes a pump carriage 50 slidable in opposite directions. When a printer head carriage moves to the left as shown and contacts a carriage arm 51, it moves while pressing the pump carriage 50. A cap 52 moves along a first rail 54 and covers a nozzle. An atmosphere opening valve 53 is installed at a back surface of the pump carriage 50. The atmosphere opening valve 53 moves to the left on opening state when touched to a second rail 55. When the pump carriage 50 stops at the end of a stroke, an atmosphere opening valve cam 56 rotates second rail 55 apart from the atmosphere opening valve 53 and the valve is shut by action of a spring. First and second pump cams 57, 58 run a suction pump 59 and make a vacuum condition. Cap 52 and an ink jet head are suctioned through a suction tube 60 connected between the suction pump 59 and the cap 52. Such conventional maintenance station has to include an arrangement of the cap, the atmosphere opening valve, the suction pump, the cams for moving such parts and the vacuum tube. Therefore, such construction is complicated and miniaturization is not easy.
The object of the present invention is to remove such defects and to provide a small maintenance station having a simple construction.